Development of radiation transport code in three-dimensional (X, Y, Z) geometry for shielding analyses by direct integration method.

Abstract

A three-dimensional radiation transport code TRISTAN has been developed by applying the method of direct integration to the group-flux calculation in order to enhance the accuracy of shielding analysis. It uses group-angle transfer matrices derived from the double-differential cross section data instead of the Legendre polynomial expansion.In order to improve the numerical accuracy, a technique to separate radiation into two components (the scattered and the unscattered) is adopted and the balance equation of radiation flux is applied to the solution method. Two new techniques, a stratification of the angular mesh and a kind of the forward-adjoint coupling, are introduced to enhance its applicability to the practical shielding analysis.The validity of the TRISTAN is verified by making comparison with the results of the Monte Carlo code MCNP, and with the experimental values in the JRR-4 streaming experiments.